Check if a number is power of 8 or not in C++

In this section, we will see, if a number is the power of 8 or not using some easier method. If a number like 4096 is there, then the program will return true, as this is the power of 8.

The trick is simple. we will calculate log8(num). If this is an integer, then n is the power of 8. Here we will use the tranc(n) function to find the closest integer of the double value.

Example

 Live Demo

#include <iostream>
#include <cmath>
using namespace std;
bool isPowerOfEight(int n) {
   double val = log(n)/log(8); //get log n to the base 8
   return (val - trunc(val) < 0.000001);
}
int main() {
   int number = 4096;
   if(isPowerOfEight(number)){
      cout << number << " is power of 8";
   } else {
      cout << number << " is not power of 8";
   }
}

Output

4096 is power of 8

Arnab Chakraborty

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Updated on: 22-Oct-2019

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